Commentary
Crab and Phil have it right. Let's put ourselves in the cockpit. Any of us who've flown offshore know exactly what was going through those pilots' minds as they tried to make it back to the beach with no transmission pressure.
Rock and a hard place? Oh boy! Landing on the cold, inhospitable sea would have been tantamount to murder, or just as bad, suicide. With this in the very front of their minds, they decided to press on: Surely this thing has *some* run dry capability. Surely! It's one of the big safety selling points of this new ship. I mean, everything I've read has mentioned it..."30-minute run-dry capability of the main gearbox." Well, no, not the RFM but those damn lawyers probably wouldn't let Sikorsky put that in official writing. But surely...
Slow down? Not bloody likely, not when time is of the essence and slowing down would've increased the amount of time it would take to get back to dry land. Go down? Yeah...but if you get really low, then VHF commo and being seen on radar become issues. So 800 feet probably seemed "low enough" to the crew, a good compromise altitude.
I'm also certain both of them had their hearts in their throats...because mine would have been, desperately hoping that I'd at least get some sign of impending doom before it all came apart - a little warning...something...enough to let me get the damn thing down on the water if I really, really had to, which wouldn't take me long from 800 feet. But if that was their thinking, they figured wrong.
We pilots simply have to come to grips with the fact that no helicopter transmission can be guaranteed to run for any length of time without oil, no matter what the manufacturer might say in their fancy four-color sales brochure. Of all the things that we can have more than one of (e.g. engines, generators, hydraulics...) the main transmission is the one thing that still *cannot* be redundified (or for you pedants, "made redundant").
The Cougar accident is a sad, sobering reminder of this truth.